Acoustic wave touch panels are known to include a substrate on which transducers are mounted in order to impart an acoustic wave traveling along a first axis of the panel and along a second axis of the panel that is perpendicular to the first axis. An array of reflective elements extends along each of the first and second axes. Each array of reflective elements reflects portions of the acoustic wave imparted into the panel along a number of parallel paths of differing lengths such that these parallel paths extend across a touch region of the panel.
Some acoustic waves require that the thickness of the substrate be thin in order to support the particular acoustic wave desired for propagation while minimizing unwanted higher order modes of the acoustic wave. One such bulk acoustic wave is a zeroth order horizontally polarized shear wave referred to as Zohps.
In order to increase the thickness of the touch panel it is known to laminate the substrate in which the shear wave is propagating to a backplate using a non-shear wave coupling adhesive. A suitable adhesive used to bond the substrate to the backplate for a shear touch panel is a silicone rubber adhesive which remains liquid-like even after curing. In order to make such a laminated panel, heretofore the liquid-like adhesive was applied to either the back surface of the substrate or the top surface of the backplate. Next, one edge of the substrate was brought into contact with one edge of the backplate with the planes of the substrate and backplate at an angle to each other. The gap between the substrate and the backplate was then closed with the same motion that one would use to close a book, the substrate and backplate being brought together slowly so as to prevent air bubbles from forming in the adhesive layer. While the method disclosed above accomplishes the broad objective of limiting if not preventing coupling between substrate and the backplate, an improved technique, particularly for the purposes of manufacturing in large quantities is needed in the lamination process. Advantageously, as opposed to the above described technique in which the adhesive is not properly constrained to any limited area of the touch panel, an improved technique would constrain the adhesive material to a limited area of the touch panel.